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  1. #1

    2003 STX-12f Hydrolocking

    New to the forum and JetSkis. I just got a great (maybe) deal on a 2003 STX-12F and have been fixing the ski as it didn't run when I got it. It looks to be in great condition, but needed a new fuel pump, with the pump replaced the ski seemed to run fine. However after running anything over 35mph and shuting the ski off it won't start back up, keep it under 35 and all is well. Then after a hour or so it will start. I thought this was most likely a battery issue so I threw a multi meter in the ski and tryed to reproduce the issue. Battery was fine, so I took the plugs out and I had water in cylinders #1 and #4.

    So my question is ( not knowing skis very well) what should I look at?? Blown head gasket? Or reversion??

    I'm having to recharge the battery so I can get all the water blown out with the plugs remove so I can restart the ski- hopefully is starts back up! Any help would be greatly appreciated.


  2. #2
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Check the compression and do a leakdown test and post back. It could be several things but its a fairly uncommon issue.

    Check to make sure you don't have anything blocking the exhaust and make sure that water exits the pisser on the right side of the ski while the engine is running.

    Sean

  3. #3
    Sean,
    Thanks for the reply. I worked on the ski this morning, unfortuately I left my compression tester in FL, so I decided to look at the exhaust side. The joint where the water box muffler connects to the exhaust mainifold is extremely corroded. I'm guessing this may have allowed reversion at higher rpms. Oil on the dipstick was clean, but it has a little whipped water/oil under the oil fill cap. I have a pair of SBC 377 in a boat that had reversion issues and it had the same syptoms. Does it sound possible to you? Have you ever heard of anyone welding a new flange on the muffler box?

  4. #4
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Mine was destroyed as well, if that's the case it may be worth replacing. High rpms would in theory prevent reversion due to the faster moving and higher volume of the exhaust gas, but that may be all that's wrong. Make sure you don't have any cracks in your fuel filler cap and tube, I know of one ski that allowed water in the fuel that way although that doesn't sound like the same problem. Pull the exhaust manifold off and check to make sure the surfaces are clean and not corroded, I had to replace my manifold and waterbox due to salt rot from the previous owners.

    Sean

  5. #5
    Sean,

    My exhaust mainifold looks good- very clean around the mating surface to the head. The exhaust pipe on the other hand was screwed! It is actually corroded through the waterjacket under the blue hose that connects the exhaust pipe to the water box muffler. I think what was happening was at higher pressures the water had enough force to get into that dry joint, then back up into the exhaust and into the cylinders. If not I have more problems. I'd hate to order a new exhaust pipe and water box then have something else letting the water in. Do you know of a good place to get used parts??

  6. #6
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Keep an eye out here in the classifieds, with exhaust parts I would only buy fresh water parts. I may know of one for sale, I'll check and get back to you.


    Post some pictures up.


    Sean

  7. #7
    I'll try and post pictures tomorrow. Do you think you could replace the head gasket with the engine still in the hull?? It's not that heavy, but I'm on a remote island with no shop.

  8. #8
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Yep but it's easier to set the cam timing out of the hull.

    Sean

  9. #9
    Click image for larger version. 

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ID:	296894Sean,

    Here are the pictures. Found new parts and have them on the way.Click image for larger version. 

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  10. #10
    Sean,

    So do you think this was my problem?? Part don't get here for another week!

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